1. Field of the Invention
The present invention relates to a method for producing a toner particle for developing electrostatically charged images in an image forming method, such as electrophotography or electrostatic printing.
2. Description of the Related Art
Recently, copiers and printers have been used in a variety of regions, and have been also used under severer environments at high temperature and high humidity, which readily reduce the amount of charging. Printers using a high-speed one-component developing scheme have been also used to satisfy requirements for a reduction in size, an increase in speed, and higher stabilization. The toner for the one-component developing scheme contacts a charging member less frequently compared to the toner for the two-component developing scheme using a carrier. Accordingly, a relatively large stress should be applied to the toner for the one-component developing scheme to be charged at a predetermined amount of charging, leading to a large load on the toner.
A toner having higher functions given by adhering a resin particle having a variety of functions to the surface of a toner base particle has been proposed. The toner can surely attain a modified surface to enhance durability, charging properties, heat resistance and the like.
Japanese Patent Application Laid-Open No. 2014-002310 has proposed a toner prepared by aggregating and fusing resin particles prepared through a phase inversion emulsion step on the surfaces of core particles. In this disclosure, the resin particles are present on the outermost surface of the toner. Such resin particles unevenly distributed may readily drop off, leading to inferior durability. The resin particles also have insufficient charging stability under a highly humid environment, which may reduce image density under a highly humid environment.
To efficiently attain a charging effect even under a highly humid environment, Japanese Patent Application Laid-Open No. 2011-137967 has proposed a toner having a surface to which resin particles containing a unit having a salicylic acid-based substituent are adhered. Unfortunately, the adhesion state of the resin particles is not controlled in particular, so that aggregates of the resin particles may adhere to the surface of the toner to reduce the durability.
For such reasons, it has been desired that resin particles are uniformly adhered to the surfaces of toner base particles without aggregation of the resin particles to attain a toner having high charging stability and durability under environments at high temperature and high humidity.